1. Field of the Invention
This invention relates to an optical recording method onto an optical recording medium containing a diacetylene derivative compound, particularly to an optical recording method employing an IR-ray laser of 800-900 nm as the optical writing means.
2. Description of the Related Art
Recently, optical discs are of primary interest among office automations. Since optical discs are capable of recording and storing a large amount of documents and literatures in one disc, documents in an office can be pigeonholed or managed with good efficiency. Various recording media have been investigated for such an optical disc, and those utilizing organic materials are attracting attention because of low price and easiness in manufacture.
As such an organic material for recording medium, a diacetylene derivative compound has been known and a recording technique employing said compound for a laser recording medium by utilizing the thermal color change property of said compound is disclosed in Japanese Laid-open Patent Application No. 14780/1981. However, in this specification, there is no description about what kind of laser has been employed or has to be used, except that there is a mere description that recording was performed by use of a laser.
The present inventors have investigated about laser recording of the diacetylene derivative compound by use of various kinds of laser and consequently confirmed that, while thermal color change recording may be feasible by use of a large scale and high output laser such as argon laser, etc., no laser recording is practiceable when a semiconductor laser of small model and relatively low output (wavelength: 800 to 850 nm) is used. However, a practical recording medium of an optical disc, etc. is desired to have a capability of optical writing with a semiconductor laser of small model and low output.
Further, the recording layer of the related art comprising the diacetylene derivative compound as described above is formed by use of fine crystalline powder of the diacetylene derivative compound, and hence the molecules of the diacetylene derivative compound are randomly oriented within the recording layer, whereby light transmittance or reflectivity may differ and the degree of the chemical reactions may vary depending on such a molecular orientation. Thus, it is not always suitable for high density recording.